Water-swellable clays, such as bentonite clay, are often slurried in water for the purpose of treating the clay in some manner. For example, water-swellable clays are slurried in water for the purpose of washing the clay for contaminant removal; for the purpose of reacting the clay, for example, to provide some ion exchange, as in peptizing, for the purpose of increasing the sodium ion or other ion content of the clay; for impregnating wool bodies, as disclosed in International Application No. PCT/F182/00029, published Feb. 3, 1983 under International Publication No. WO 83/00369, and as disclosed in my prior application Ser. No. 530,430 filed Sept. 8, 1983, now U.S. Pat. No. 4,514,510, for hydrogen ion exchange with a suitable hydrogen ion exchange resin for the purpose of reducing the acid demand of the clay. In each case, after treatment of the clay in water slurry form, the clay or impregnated article then is dried to a moisture content of 0-10% by weight.
The water-swellable clays are in a fully swollen form when in the water slurry and, therefore, in order to pump or otherwise transport the water-swellable clay slurry for further treatment, such as drying, the maximum clay solids content of the slurry, prior to the present invention, was approximately 5% clay by total weight of slurry. Any attempts to pump or otherwise transport a water-swellable clay slurry having a solids content greater than about 5% by weight have been unsuccessful because the clay slurry, including fully hydrated clay at a solids content greater than about 5% by weight, is much too viscous for transport and for effective homogenous treatment. As shown in the Hurd U.S. Pat. No. 2,431,481, typical prior art water-swellable clay slurries include a solids content of about 2.5 to 4.6% by weight solids for treatment such as ion exchange.
Further, in the environment of water-swellable clay slurry impregnation of mineral wool bodies, as disclosed in No. PCT/F182/00029, where pumping of the clay slurry is for only a short, recirculation distance, the clay content of the slurry is at most 10% by weight since, at higher levels, the viscosity of the slurry is too high causing a clay sediment on the surface of the mineral wool article, preventing further impregnation.
As set forth in this assignee's prior U.S. Pat. No. 4,279,547 and the McGoarty U.S. Pat. No. 4,316,833, certain organic solvents have the property of inhibiting the swelling characteristics of water-swellable clays, such as bentonite. Other prior art teaches that particular additives such as the high molecular weight polymers, such as polyacrylic acid, polyacrylamide and the like increase the swellability and viscosity characteristics of a water-swellable clay dispersion, such as disclosed in this assignee's prior U.S. Pat. Nos. 3,986,365; 4,084,382; and 4,087,365. The polymers and copolymers added for the purpose of increasing the water swellability of the water-swellable clays generally are very high molecular weight polymers, e.g. 200,000 to 2 million or more molecular weight, are added in a relatively small percentage and remain with the clays in a high molecular weight form in order to continue to beneficiate the clay to achieve a higher viscosity of the clay in water.